[I have read How to debug a mapping? and although that is a great starting point I am still clueless why this does not work.]
2* to search for the next occurence of the previous word in combination with the current word.
I have defined it in my vimrc in the following way:
nnoremap 2* hevgeb"zy/\<<C-R>z\><CR>
but pressing 2* ignores this mapping and searches for the 2nd occurence of the current word.
:map 2* shows that the keys are mapped correctly:
n 2* * hevgeb"zy/\<<C-R>z\><CR>
2* on a new line and thereby proves that the keys are not intercepted, vim receives the keys as expected.
Leaving out the 2 remaps asterisk as expected and shows that
hevgeb"zy/\<<C-R>z\><CR> does what it's intended to do. I am not happy with this implementation because it changes a register (z) but surprisingly I have not found an easy way to avoid that.
In a different mapping 2 followed by tab to show a table of contents works some times and some times not, but pressing it several times eventually triggers it:
nnoremap 2<Tab> :exec '!grep --color=always --line-number -E "^[[:space:]]*((class\|def) +([A-Za-z0-9_]+)\|\# (===\|---).*)"' shellescape(@%, 1) " \| less -R"<cr>
Based on that experience I have tried pressing
2* and here, too, it works in some cases. But what's annoying for the 2tab mapping is not acceptable for the 2* mapping because it moves the cursor.
Does somebody know in which circumstances these mappings work and in which not and how to trigger them reliably? I thought that pressing escape before might help but it does not. Sometimes it works, sometimes it does not.